13.1 History of CAC-A
Stephanie Oostman
The use of carbon rods make a sizeable impact in welding’s history in 1800 with Sir Humphrey Davy who created an arc between to carbon rods and again 1881 with Nikolay Benardos & Stanisław Olszewski who used that discovery to create Carbon Arc Welding (CAW). The use of carbon rods have been the kick off of welding. But they were late in the game when it came to their use as a cutting process. Air carbon arc cutting originated in the 1940’s. The process was used to cut away rivets in the overhead and vertical positions in hopes that gravity would then assist with the molten material to drop from place. This was a time consuming and erratic process. Not only was the molten dross or sparks unpredictable, but the rivets would not always fall away as planned. Sometimes they would reweld themselves back in place. (The History of Welding, 2020)
In 1948 a local Washingtonian named Myron Stepath added compressed air to the carbon arc process (Arcair, 2010). The streams of high-pressurized compressed air act as a blower to push the molten dross, sparks, and material to be removed, away from the cutting area. This not only was more efficient but allowed the workers to increase their speed and expand the process to flat positions as well. The process then became known as air arc cutting (aac). AAC required two workers, one to operate the carbon arc, and the other to operate the compressed air needed to blow away the molten metal.
In 1956 the process was then refined even further with the development of the electrode holder we use today (Arcair, n.d.). This development brought the compressed air stream into an easy to use handheld electrode holder, eliminating the need for two people for the job.
Basics of the process
Carbon Arc is an electric arc process where the heat generated from the arc of a carbon electrode melts the base metal it comes in contact with. Carbon arc welding is one of the oldest versions of welding, and in its day was called atomic hydrogen carbon arc welding or AHW for short (“Atomic Hydrogen Welding,” 2023). However, CAW aka AHW has become largely obsolete. The cutting technique (CAC) which uses carbon electrodes to cut and gouge parent material is still very popular in fabrication, welding and thermal cutting industries today.
Carbon arc cutting is used to cut away unwanted material by means of a carbon coated consumable rod or electrode held in the jaws of a holder that looks very similar to the holder used in shielded metal arc welding (SMAW). There are a few key differences with the equipment and the process. The biggest is, that unlike welding where we are adding metal, CAC-A removes metal, welds, cracks and helps bevel grooves in fit up operations.
The bottom or lower jaw of the holder used in carbon arc cutting has a head that rotates to insure accuracy and is outfitted with several holes in the head for the compressed air to pass through. Recall that compressed air is needed to blow away molten metal from the cutting area. There is an air valve on the handle to turn the air on or off to the head. When positioned correctly and with the right air pressure, the compressed air then blasts the molten metal away from the site directly under the electrode.
There is no shielding gas used or needed, but as the carbon rod is consumed it produces both carbon monoxide and carbon dioxide gas which is also blasted away by the air stream. Because this process uses carbon electrodes, carbon deposits are left behind on the surface metal. It is important to take care in cleaning the surface afterwards with a grinder to avoid brittleness and cracking should the area need to be rewelded, or backwelded.
Carbon arc cutting does not require that the carbon electrode react to the base metal. Which allows for more versatility than oxy-acetylene cutting (OAC), which is only effective on metals that can be oxidized. Stainless steel, carbon steel, titanium, copper alloys, nickel alloys, and aluminum alloys are just a few of the materials an individual may use CAC-A process with.
Carbon arc cutting can be used in all positions. The process can be done fully manual or semi-automatic when connected to a carriage or machine that controls the speed and movements. The cutting process requires a constant current (CC) power source capable of an operating voltage of at least 28 volts or higher. Carbon arc cutting can be operated with AC or DCEP, however DCEN should be avoided, as the arc is too unstable.
Uses of CAC-A in industry today
- Boilermakers
- Railway
- Steel mills
- Steel Fabrication
- Construction
- Chemical and Petroleum industry
- Casting finishing
- Mining industry
- Foundries
- Lumber industry
- Military
The streams of high-pressurized compressed air act as a blower to push the molten dross, sparks, and material to be removed, away from the cutting area. This not only was more efficient but allowed the workers to increase their speed and expand the process to flat positions as well.